Refrigeration systems usually include an evaporator, a condenser, a compressor, an expansion valve and a controller. Typically, in a residential air conditioning system, the evaporator and controller is located inside, the condenser and compressor are located outside and the expansion valve is located inside between an outlet of the condenser and an inlet of the evaporator. The expansion valve regulates the flow rate of a refrigerant through the evaporator to obtain a desired temperature in a space to be cooled, or cooling space.
The controller can be programmed to control operation of the refrigeration system based on inputs from various temperature and pressure sensors to obtain the desired temperature in the cooling space. Opening and closing of the expansion valve, for example, may be controlled by the controller based on a measured temperature differential across the evaporator. This temperature differential is commonly referred to as a superheat.
Formerly, the method of measuring superheat was to subtract an evaporator coil inlet temperature from an evaporator coil outlet temperature. This method, however, was often inaccurate or unresponsive to changes. Accordingly, an improved method of determining superheat and, therefore superheat error, was needed to provide a more dynamic and accurate superheat measurement. One such improved method that was developed for measuring superheat converts a measured coil outlet pressure at the evaporator to a Saturated Vapor Temperature (SVT), which is based upon a specified refrigerant, and subtracts that result from the measured evaporator coil outlet temperature. A pressure transducer may be attached to the outlet of the evaporator coil to obtain the coil outlet pressure for the superheat measurement. Though an improved superheat measurement can now be determined, existing refrigeration systems have not advantageously employed the improved superheat measurement to control operations thereof.
Accordingly, what is needed in the art is a refrigeration system that is responsive to dynamic superheat error measurements. More specifically, what is needed in the art is a refrigeration system with an improved equipment protection system that responds quickly to changes in system loads and ambient conditions.